This invention concerns a method and apparatus for the enhancement of radiographs. More particularly, it relates to a technique of intravenous angiography in which a subtracted, digitized image is processed to enhance contrast.
Conventional radiographs (x-ray pictures) are often unable to give a clear picture of the anatomical areas under study for a number of reasons. Differences in opacity between the subject and its surroundings may be so minute as to make difficult the production of an image which relies on differential opacity. Moreover, other anatomical structures may obscure the subject structure.
In order to obtain useful radiographs of certain anatomical areas such as arteries and the like, a radiographic contrast medium is typically introduced into arteries by direct puncture of an artery and insertion of a needle or catheter. This technique, called catheter angiography, renders these areas visible on x-ray photographs or radiographs but suffers from complexity and a low but statistically definite risk of complication and death. Prior to the development of the technique of catheter angiography in 1953, and from time to time subsequently, intravenous angiography has been attempted. In contrast to catheter angiography, the introduction of radiographic contrast medium in intravenous angiography is accomplished by a simple and safe venal injection rather than the direct puncture of an artery. The intravenous technique has been subject to repeated problems because of the limited amount of contrast material that enters the arteries following circulation through the heart and lungs.
Attempts have been made to obtain improved images of anantomical parts by taking a multiplicity of x-ray measurements from many different angles and mathematically combining those measurements to create a three-dimensional representation of the subject anatomical part. These three-dimensional or tomographic techniques as they are known in the art are costly and complex because they require a multiplicity of x-ray measurements as well as the related computer software and storage to process the information contained therein.
The present invention obviates the need for costly and complex tomographic equipment and substitutes in its stead a simple, inexpensive and efficient method of enhancing radiographs by means of a subtracted radiographic image which is digitally processed to enhance contrast.